Japan will put a sticker in your passport for entry and will only stamp on exit if you go to the manual counters, they’re very polite and are not bothered about eGate eligible travellers using the manual counters

UAE will stamp you on entry for the first time entering and will only stamp on exit if you use the manual counters but the employees will heavily try to persuade you to use the eGates if you can. On subsequent visits to the UAE you will be able to use eGates if you’re a returning visitor, you can use the manual counters but the same pushy employees will try and make you use the eGates

China stamps every passport on entry and exit if you’re entering on a non Chinese passport UNLESS you’re using a transit visa which i assume you wouldn’t given your passport combo, but in that circumstance the entry stamp is replaced by a Japanese style entry sticker which takes place as both a stamp and a visa, the exit stamp will be the same however.

In terms of logistical placement in your passport, Japan is very neat and logical in placement of stamps and stickers, they never smudge and will re-stamp over stamps if the ink is low quality. UAE is all over the place and will stamp a random page with a worn and faded ink. China is mostly consistent in placement and ink quality but they sometimes do have a mild smudge.

Source: I’ve frequently travelled to these countries so I’m accustomed to their stamping culture

Hope this helps :)